STY: isort

Author: jbrockmendel

pandas/_libs/reduction.pyx

@@ -5,8 +5,6 @@ from cpython.ref cimport Py_INCREF
 
 from libc.stdlib cimport malloc, free
 
-from pandas.core.dtypes.generic import ABCMultiIndex
-
 import numpy as np
 cimport numpy as cnp
 from numpy cimport (ndarray,
@@ -494,7 +492,8 @@ def apply_frame_axis0(object frame, object f, object names,
         object piece
         dict item_cache
 
-    if isinstance(frame.index, ABCMultiIndex):
+    if frame.index.nlevels > 1:
+        # MultiIndex
         raise InvalidApply('Cannot modify frame index internals')
 
     results = []
@@ -626,7 +625,7 @@ def compute_reduction(arr, f, axis=0, dummy=None, labels=None):
 
     if labels is not None:
         # Caller is responsible for ensuring we don't have MultiIndex
-        assert not isinstance(frame.index, ABCMultiIndex),('MultiIndex type')
+        assert frame.index.nlevels == 1
 
         # pass as an ndarray/ExtensionArray
         labels = labels._values

pandas/core/apply.py

@@ -5,15 +5,13 @@
 from pandas._libs import reduction as libreduction
 from pandas.util._decorators import cache_readonly
 
-from pandas.core.dtypes.generic import ABCMultiIndex
-
 from pandas.core.dtypes.common import (
     is_dict_like,
     is_extension_array_dtype,
     is_list_like,
     is_sequence,
 )
-from pandas.core.dtypes.generic import ABCSeries
+from pandas.core.dtypes.generic import ABCMultiIndex, ABCSeries
 
 
 def frame_apply(